The present invention relates to a concrete injection plug for repairing a concrete construction, and to a method for injecting a remedial concrete material into a portion of the concrete construction.
Degradation of concrete material of a concrete construction is a considerable problem. The degradation may be caused by a secular change in the material per se, neutralization of the concrete due to external circumstance, injury from salt, alkali-aggregate reaction, unsatisfactory work or execution, shrinkage due to drying, generation of crack or peeling-off due to vibration from vehicles or an earthquake. A reduction in the mechanical strength of reinforcements due to their rusting accompanied by the peeling-off is also a source of degration. The degradation of the concrete may also include separation of a furring mortar formed over the concrete body therefrom, which in turn leads to falling of the skin tiles of a building formed over the furring mortar, or separation and falling of an internal concrete wall of a railway tunnel or the like, or water leakage from a dam.
Also, a separation space layer may be formed between an inner concrete body and an outer mortar layer at a position from 2 to 3 cm from a wall surface. A typical thickness of the separation space layer is in a range of from 0.2 to 1 mm. In order to repair a wall containing such a separation space layer, epoxy resin or a cement slurry injection method has been widely carried out in order to fill the space therewith.
According to a conventional epoxy resin injection method, an injection hole having a diameter of about 5 mm and reaching the separation space layer is formed on the wall by means of a drill. Then, a sleeve tip of a grease pump is depressed into the injection hole so as to directly inject the high pressure epoxy resin thereinto. Alternatively, an injection plug formed of a plastic material is adhesively fixed to the injection hole of the wall, and the pressurized epoxy resin is injected by a compressor or a manual pump. In both cases, any crack portions observed on a surface of the wall, other than the injection hole, are sealed by a sealant.
On the other hand, the above described high pressure grease pump cannot be used for the injection of the cement slurry, since the latter has relatively low viscosity. For example, if the grease pump capable of providing high fluid pressure such as 30 kg/cm.sup.2 is used, the cement slurry may be leaked through a minute gap defined between the injection hole and the tip end of the sleeve of the pump, to thereby render the pressurization impossible. To this effect, a low pressure injection method is applied where a pressure of not more than 5 kg/cm.sup.2 is applied for the injection of the cement slurry. Incidentally, this low pressure injection method is also available for the epoxy resin.
In case of the low pressure injection method for injecting the cement slurry or the epoxy resin, the injection hole is formed on the concrete wall by means of a drill, and a flange portion of the plastic plug is adhesively fixed to a position around the injection hole. Further, an injection hose extending from the injection pump is engaged with a rear mouth piece portion of the plastic plug, so that the cement slurry or the epoxy resin is injected under pressure through the injection hole into the desired internal crack portion of the concrete wall.
This plastic plug has a funnel shape having a diameter of about 5 cm and is readily available. Adhesive material is used for fixing the plug to the wall surface. However, since the adhesive force is insufficient preventing the plug from being separated from the wall during pressurized injection, additional operators are required for pressing the plug onto the wall surface in addition to an operator for operating the pressure pump.
In order to dispense with the worker who has to press the plug onto the wall surface, anchor type injection plug (hole-in-anchor type injection plug) have been employed. This plug has an anchoring or wedge function. Therefore, the anchor type injection plug can be fixedly secured to the wall by hammering the plug into the drilled injection hole. Thus, a release of the injection plug from the wall is avoidable even during the injection work.
With the above described low pressure injection method using the conventional injection plug, it would be difficult to perform injection of the cement slurry in comparison with the injection of the epoxy resin. Therefore, in injecting the cement slurry, injection holes are formed at many places corresponding to portions where the separating of the mortar is deemed to occur. Therefore, it requires much labor and time. In the worst case, epoxy resin must be used instead of the cement slurry for the concrete repair, where many injection holes cannot be located.